Update CONTRIBUTING.md
new quickstart

updated readme to have an up to date quickstart!
Rewrite README.md
Specify language for syntax highlighting in code blocks
Bump version number to v0.4.0
Merge branch 'master' into dev

* master:
  new quickstart
  Update CONTRIBUTING.md
Refactored FilePreProcessor in preparation for #140
Refactored out #r directives from resulting script and pass them to the ScriptEngine. Fixes #140
Added some checks for existing references and usings and removed redundant adding of loaded script
Added logging statements
Merge branch '140' of github.com:khellang/scriptcs into 140